Evolution of the radio access scheme and the radio network for cellular mobile communication (hereinafter referred to as “Long Term Evolution (LTE)” or “Evolved Universal Terrestrial Radio Access (EUTRA)”) has been studied by the 3rd Generation Partnership Project (3GPP). According to LTE, as a communication scheme for radio communication from a base station device to a mobile station device (downlink), the Orthogonal Frequency Division Multiplexing (OFDM) scheme which is a multicarrier transmission scheme is used. Also according to LTE, as a communication scheme for radio communication from a mobile station device to a base station device (uplink), the SC-FDMA (Single-Carrier Frequency Division Multiple Access) scheme which is a single-carrier transmission scheme is used.
According to LTE, HARQ (Hybrid Automatic Repeat reQuest) is used, by which the data failed to be decoded on the receiving side is not discarded but combined with retransmitted data and then decoded. The base station device uses an uplink grant (UL grant) transmitted on a PDCCH (Physical Downlink Control Channel) and an HARQ indicator transmitted on a PHICH (Physical HARQ Indicator Channel), to instruct the mobile station device to perform initial transmission or retransmission of a PUSCH (Physical Uplink Shared Channel) that is a channel for transmitting uplink data (or referred to as an “uplink shared channel (UL-SCH)” or a “transport block”).
The base station device receives the PUSCH transmitted by the mobile station device. The base station device transmits, on a PHICH (Physical HARQ Indicator Channel), the HARQ indicator indicating whether uplink data has been successfully decoded or not. The HARQ indicator indicates ACK (ACKnowledgement) or NACK (Negative ACKnowledgement). When the base station device succeeds in decoding uplink data, the HARQ indicator indicates ACK. When the base station device fails to decode uplink data, the HARQ indicator indicates NACK. When the HARQ indicator received on the PHICH indicates NACK or when retransmission of the PUSCH is instructed by an uplink grant, the mobile station device retransmits the PUSCH. The base station device can set the maximum number of times of transmitting uplink data for the mobile station device. When the number of times of transmitting uplink data reaches the maximum number of times of transmission, the mobile station device deletes the uplink data from the HARQ buffer.
The 3GPP has also studied a radio access scheme and a radio network that use a plurality of transmission/reception antennas in a frequency band wider than LTE and an uplink to implement still faster data communication (hereinafter referred to as “Long Term Evolution-Advanced (LTE-A)” or “Advanced Evolved Universal Terrestrial Radio Access (A-EUTRA)”). LTE-A requires backward compatibility with LTE. In other words, LTE-A requires that a base station device of LTE-A should communicate by radio with both a mobile station device of LTE-A and a mobile station device of LTE simultaneously, and that a mobile station device of LTE-A should be able to communicate by radio with both the base station device of LTE-A and the base station device of LTE. Also, LTE-A has studied use of the same channel structure as that of LTE.
According to LTE-A, use of MIMO (Multiple Input Multiple Output) SM (Spatial Multiplexing) for the PUSCH has been studied in order to improve the use efficiency of an uplink frequency. By using MIMO SM, the mobile station device can spatially multiplex a plurality of uplink data into one PUSCH and transmit the data. Non Patent Document 1 discloses that HARQ is performed independently for each of the plurality of uplink data transmitted on the same PUSCH. In order to perform HARQ independently for each of the plurality of uplink data transmitted on the same PUSCH, the base station device transmits an HARQ indicator for each uplink data, and transmits the same uplink grant including the information related to HARQ that indicates initial transmission or retransmission for each uplink data. Non Patent Document 2 proposes to perform an independent HARQ process for each of the plurality of uplink data spatially multiplexed into the same PUSCH, when MIMO SM is used for an uplink.
Non Patent Document 3 proposes that the information included in an uplink grant (UL grant) that can give an instruction to transmit a plurality of uplink grants on the same PUSCH is set at specific code points (values), thereby disabling a part of the uplink data. When a part of the uplink data is disabled by the base station device, the mobile station device transmits, on the PUSCH, uplink data that has not been disabled in accordance with the received uplink grant.